This invention relates to a system for applying an ultrasonic probe to the surface of a living body to measure the reflected ultrasonic waves therefrom and thereby obtain an ultrasonic tomographic image, or determine a velocity of flow of the blood, and more particularly to a measurement apparatus using a measurement signal from a portion, which moves periodically due to the cardiac motion, of a living body.
In a diagnosis apparatus, it is greatly necessary to obtain information from a moving region of interest. Regarding, for example the heart, various diagnosis information of a high accuracy cannot be obtained without taking the influence of the cardiac motion into consideration. In order to meet these requirements, a measurement method utilizing an electrocardiogram as a synchronizing signal, i.e. the periodicity of a cardiac motion is widely used.
For example, the thesis entitled "Gated Cardiac Computed Tomography with a Motion Phantom" in the "Radiograph", Vol. 134, pp 213-217, points out that a clear stop motion cardiac image can be obtained by repeatedly collecting the special-phase data alone in a cardiac cycle in the X-ray computed tomography, and thereby reconstructing the image.
In the ultrasonic radiography, the real time imaging is required, and repeatedly collecting special-phase data in a cardiac cycle so as to obtain one picture is contradictory to this purpose. In an apparatus for measuring a flow rate of the blood in the heart or a blood vessel in the vicinity of the heart, the moving speed of the heart or blood vessel is superposed on the flow rate of the blood, and an object to be measured goes out of the visual field of measurement due to the cardiac motion in some cases.